Process for forming a dispersion of polytetrafluoroethylene

Abstract

A process for forming a dispersion of polytetrafluoroethylene particles in a liquid containing a dispersant by passing the mixture through a plurality of nozzles within a liquid-jet interaction chamber at a pressure of to deagglomerate and stabilize the polytetrafluoroethylene particles.

What is claimed is: 
     
       1. A process for forming a dispersion of dry polytetrafluoroethylene particles in an organic carrier fluid comprising the steps of: (a) surface functionalizing the polytetrafluoroethylene particles having an average primary particle size of less than 1 micron with electron beam or gamma irradiation of at least 4 Mrad in the presence of atmospheric oxygen and water or selecting polytetrafluoroethylene particles having an average primary particle size of less than 1 micron that have been subjected to electron beam or gamma irradiation of at least 4 Mrad in the presence of atmospheric oxygen and water to functionalize the particle surface;   (b) mixing the irradiated particles with the liquid and at least one dispersant in an amount sufficient to stabilize the dispersion to form a mixture;   (c) passing the mixture, at least once, through a plurality of nozzles within a liquid-jet interaction chamber at a pressure of at least 1000 psi to deagglomerate the polytetrafluoroethylene particles.   
     
     
       2. The process of claim 1 wherein the average primary particle size of the polytetrafluoroethylene particles is about 0.25 microns or smaller. 
     
     
       3. The process of claim 1 wherein the irradiation is carried out at least 8 Mrad. 
     
     
       4. The process of claim 1 wherein the dispersant is characterized in that it has a molecular structure having an interacting group which can interact with the surface-functionalized particles, a solubilizing group which can interact with the carrier fluid of the dispersion and a sufficiently high molecular weight to provide effective steric stabilization for the dispersed particles. 
     
     
       5. The process of claim 1 wherein the carrier fluid is a lubricant. 
     
     
       6. The process of claim 1 wherein the carrier fluid is selected from the group consisting of paraffinic and naphthenic mineral oils, hydrocracked mineral oils, solvent refined oils, and blends of these oils, aromatic and aliphatic hydrocarbons, polyalphaolefins, hydrogenated polyalphaolefins, alkylated aromatics, esters, diesters, polyol esters, and complex esters, phosphate esters, dihydrocarbyl carbonates, ethers, polyalkylene glycols, perfluoroalkyl polyethers, silicone fluids, silahydrocarbons, alcohols, ketones, amines, and heterocyclic compounds, N-methyl pyrolidinone, isophorone, and tetrahydrofuran and mixtures of any combination of these. 
     
     
       7. The process of claim 1 wherein the dry polytetrafluoroethylene particles are dispersion polymerized particles.